Harold Loeb was born in New York City. His father Albert Loeb was an investment banker with the firm Kuhn, Loeb & Company, and his mother Rose was born a Guggenheim: Peggy Guggenheim was a cousin. Loeb graduated from Princeton University in 1913 and then went to Alberta, Canada, where he worked on a ranch and did other physical labor. In 1914, he returned to New York, where he married Marjorie Content, daughter of a wealthy stockbroker. The couple had two children and lived in rural Alberta for a while, until the outbreak of World War I necessitated their return to the USA. After the war, he became part owner of an avant-garde bookstore, The Sunwise Turn. Through the store, he met a number of writers, including F. Scott Fitzgerald and Malcolm Cowley. In 1921, Loeb separated from his wife and co-founded Broom, a literary magazine, moving to Rome to begin publishing it in Europe for the sake of economy. He edited and published early works by Marianne Moore, Hart Crane, Wallace Stevens, William Carlos Williams, and E. E. Cummings, among others. A couple of years later, he left Broom and moved to Paris to focus on his own writing. There he met other American expatriates, including writers and artists such as Ernest Hemingway. He had an affair with Lady Duff Twysden and accompanied Hemingway and his circle to the bullfights in Pamplona in 1925. Hemingway later used thinly-disguised versions of them as the characters of Robert Cohn and Lady Brett Ashley in his novel The Sun Also Rises. Loeb published his first two novels, Doodab (1925) and Professors Like Vodka (1927) while living in Paris. He continued to write after he returned to New York in 1929. He published two non-fiction books in the 1930s, and essays about writers Ford Madox Ford and Hemingway and their times in Paris. His memoir The Way It Was appeared in 1959.